This invention relates generally to a self-contained power subsystem, and, more particularly to a self-contained power subsystem for use in missiles and re-entry vehicles and the like and which operates in response to low power level commands.
Many airborne systems such as missiles and re-entry vehicles require subsystems to power control devices in response to low power level commands. These subsystems are normally self-contained since there is usually no external source of power available when the vehicle is airborne. A self-contained power subsystem stores a finite amount of energy until it is needed and then meters the energy to control devices where useful work is performed in response to commands from a separate control subsystem. The energy is stored in a convenient form of chemical, potential or kinetic energy and transformed to the form required by the control devices when it is needed.
The control devices must meet certain performance requirements. These requirements unfortunately place substantial restrictions on the form of the energy required by the control devices. For example, a fast response control device may require energy in the form of a pressurized incompressible fluid to meet certain performance requirements with the current design now in use.
The finite amount of energy that must be stored within the subsystem depends on many factors including the amount of energy that is lost or wasted in obtaining the useful work. The size and weight of the power subsystem depends on the amount and form of the stored energy and the bulk and complexity of the components required to transform the stored energy and control the useful work performed.
In many advanced airborne systems presently in use, severe restrictions are placed on the allowable size and weight of the power subsystem, however, above-average performance is still required. This is particularly true for certain classes of small re-entry vehicles where, in addition, the power subsystem must remain dormant for months or years with no maintenance and then reliably perform a significant amount of useful work over a relatively short period of time (say 30 seconds) responding to commands in a precise manner.
Any self-contained power subsystem basically is a combination of energy storage devices, energy conversion devices, and energy output/control devices. Over the years an almost infinite variety of subsystem concepts have been designed and used in airborne systems with varying degrees of success. The most successful, as a class, are those that store chemical energy using batteries, liquid fuels or solid propellants and convert this energy to controlled mechanical work. All tend to share certain common characteristics:
(1) The stored energy must be converted to another form so that the mechanical work can be precisely controlled, PA1 (2) the energy conversion devices tend to be bulky and heavy, and PA1 (3) a significant amount of maintenance is required even when the subsystem is dormant. PA1 1. The operating time is less than approximately 1 minute; PA1 2. The hydraulic fluid consumption is less than approximately 200 cubic inches; and PA1 3. Precise servo-actuator performance is desired.
Significantly, all concepts tend to work equally well for 30 seconds or 30 hours; it is primarily a matter of initially storing more energy for longer periods of operation and performing more maintenance.
What is needed is a subsystem that is extremely small and lightweight, requires no maintenance for long periods of time and, when activated, will reliably perform controlled mechanical work for a relatively short period of time in a precise manner.